US6629520B2 - Ignition apparatus for internal combustion engine - Google Patents

Ignition apparatus for internal combustion engine Download PDF

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US6629520B2
US6629520B2 US09/984,453 US98445301A US6629520B2 US 6629520 B2 US6629520 B2 US 6629520B2 US 98445301 A US98445301 A US 98445301A US 6629520 B2 US6629520 B2 US 6629520B2
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spark
ignition
discharge
supply
signal
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US20020056445A1 (en
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Hiroshi Inagaki
Daisuke Nakano
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Niterra Co Ltd
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NGK Spark Plug Co Ltd
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Assigned to NGK SPARK PLUG CO., LTD. reassignment NGK SPARK PLUG CO., LTD. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: NAKANO, DAISUKE, INAGAKI, HIROSHI
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02P—IGNITION, OTHER THAN COMPRESSION IGNITION, FOR INTERNAL-COMBUSTION ENGINES; TESTING OF IGNITION TIMING IN COMPRESSION-IGNITION ENGINES
    • F02P3/00—Other installations
    • F02P3/02—Other installations having inductive energy storage, e.g. arrangements of induction coils
    • F02P3/04—Layout of circuits
    • F02P3/045—Layout of circuits for control of the dwell or anti dwell time
    • F02P3/0453—Opening or closing the primary coil circuit with semiconductor devices
    • F02P3/0456—Opening or closing the primary coil circuit with semiconductor devices using digital techniques

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  • the present invention relates to an ignition apparatus for an internal combustion engine in which a spark plug receives high voltage for ignition generated from a secondary winding of an ignition coil upon intermittent supply of primary current to a primary winding thereof, such that the spark plug produces spark discharge in order to burn a fuel-air mixture.
  • Spark energy which an internal combustion engine requires for proper burning of a fuel-air mixture has been known to change depending not only on the type of internal combustion engine, but also on operation conditions such as engine speed and engine load. Spark energy can be represented by the product of the magnitude of discharge current flowing as a result of spark discharge and the duration of the spark discharge.
  • the requisite spark energy varies depending on the air-fuel ratio of the fuel-air mixture. For example, when an internal combustion engine is operated with a lean fuel-air mixture having an air-fuel ratio of 20 or more as in the case of a lean burn engine, the density of fuel is low, and consequently the fuel-air mixture has low ignitability. Therefore, the spark energy must be increased.
  • a conventional ignition apparatus for an internal combustion engine is designed such that insufficient spark energy does not arise; i.e., the ignition apparatus supplies the maximum spark energy required under various operation conditions of the internal combustion engine.
  • the above-described conventional ignition apparatus has the following drawbacks.
  • a state in which an internal combustion engine can be operated by spark energy lower than the maximum spark energy e.g., during high-speed, heavy-load operation
  • supply of spark energy becomes excessive, and the excessive spark energy does not improve the ignitability but accelerates consumption of the spark plug electrodes.
  • the speed of turbulent flow of fuel-air mixture increases, and thus, a so-called multiple discharge phenomenon occurs easily. That is, in such a state, spark is caused to flow toward the downstream side during a second half of the spark discharge in which spark energy decreases, the spark discharge is then interrupted, and another spark discharge is generated again.
  • a so-called full-transistor igniter has been widely used for an internal combustion engine.
  • a semiconductor device such as a power transistor is used as a switching element for intermittently supplying electricity to a primary winding of an ignition coil in order to apply high voltage for ignition to a spark plug.
  • ignition timing the duration of supply of electricity to the primary winding before spark discharge (ignition timing) is controlled (i.e., the drive duration of the switching element is controlled) in accordance with operation conditions of the internal combustion engine, the amount of magnetic flux energy which is accumulated in the ignition coil to be used as spark discharge can be controlled to a level required for combustion of the fuel-air mixture.
  • the present inventors proposed an ignition apparatus for an internal combustion engine which, instead of controlling the duration of supply of electricity to the primary winding of an ignition coil before spark discharge, resumes supply of electricity to the primary winding during spark discharge by use of spark-discharge interruption switching means, to thereby stop spark discharge.
  • this ignition apparatus for an internal combustion engine it becomes possible to interrupt spark discharge after elapse of a spark discharge duration suitable for operation conditions of the internal combustion engine, while maintaining high voltage for ignition generated at the secondary winding through intermittent supply of electricity to the primary winding. In this manner, the amount of spark energy can be controlled to a proper level.
  • the primary current flows continuously after supply of the primary current is resumed for the purpose of interrupting spark discharge, the amount of heat generated by the spark-discharge interruption switching means increases, and power is needlessly consumed. Therefore, the supply of electricity is desirably stopped at a proper timing. However, if the primary current flowing after resumption of electricity supply is stopped abruptly, spark discharge is generated again, thereby impairing operation of the internal combustion engine.
  • the power source voltage output from a power source unit varies at the time of startup of the internal combustion engine or due to improper operation of a generator, resulting in variations in the amount of magnetic-flux energy accumulated in the ignition coil. That is, when the power source voltage output from the power source unit of the internal combustion engine exceeds its rated value, a larger current flows through the primary winding than in an ordinary state, with the result that an excessive amount of magnetic-flux energy is accumulated in the ignition coil.
  • the present invention has been accomplished in view of the above-described problems of the prior art. It is therefore an object of the present invention to provide an ignition apparatus for an internal combustion engine which, without controlling the duration of supply of electricity to the primary winding of an ignition coil before spark discharge, minimizes the amount of spark energy supplied to a spark plug to thereby suppress needless consumption of the spark plug and which can prevent breakage of constituent components, which would otherwise occur due to variation in the amount of magnetic-flux energy accumulated in the ignition coil.
  • an ignition apparatus for an internal combustion engine comprising: a DC power source unit; an ignition coil having a primary winding through which primary current flows upon application to the primary winding of power source voltage from the DC power source unit, and a secondary winding which forms a closed loop in cooperation with a spark plug attached to the internal combustion engine; switching means connected in series to the primary winding and adapted to interrupt and resume the primary current flowing through the primary winding; and ignition control means for outputting an ignition command signal for controlling ignition timing, the ignition command signal causing the switching means to interrupt and resume the primary current flowing through the primary winding in order to generate at the secondary winding high voltage for ignition to thereby cause the spark plug to generate spark discharge, wherein the ignition apparatus further comprises: spark-discharge duration time setting means for setting a spark-discharge duration time on the basis of operation conditions of the internal combustion engine, the spark-discharge duration time representing a period during which spark discharge of the spark plug is to be maintained; spark-discharge interruption control
  • the spark-discharge duration time setting means sets, on the basis of operation conditions of the internal combustion engine, a spark-discharge duration time necessary for burning a fuel-air mixture; and the spark-discharge interruption control means controls the spark-discharge interruption command signal in accordance with the spark-discharge duration time.
  • the spark-discharge interruption circuit is operated in accordance with the spark-discharge interruption command signal in order to resume supply of primary current to the primary winding to thereby interrupt spark discharge of the spark plug.
  • the ignition apparatus for an internal combustion engine interrupts spark discharge by resuming the supply of primary current to the primary winding and thus controls spark energy supplied to the spark plug in accordance with operation conditions of the internal combustion engine. It is noted that when the supply of primary current is resumed during spark discharge, the magnetic flux energy which has been decreasing with consumption of the electromotive force generated at the secondary winding is apt to increase, with the result that the ignition coil generates an electromotive force in a direction which maintains decreasing magnetic flux energy decreasing (i.e., a voltage having a polarity opposite that in effect at the time of spark discharge). Thus, spark discharge is interrupted.
  • the period for supplying electricity to the primary winding before spark discharge is set long in order to accumulate sufficient magnetic flux energy in the ignition coil. Therefore, a high voltage can be generated at the secondary winding for ignition which has a magnitude sufficient for generating spark discharge reliably under any operation condition of the internal combustion engine.
  • the spark-discharge duration time is controlled in accordance with operation conditions of the internal combustion engine, supply of excessive spark energy to the spark plug can be prevented.
  • the spark-discharge duration time is shortened in order to cause the spark plug to reliably generate spark discharge through application of high voltage for ignition thereto, while suppressing excessive supply of spark energy to the spark plug to thereby suppress generation of multiple discharge.
  • the spark-discharge duration time is increased in order to reliably burn the fuel-air mixture.
  • spark-discharge duration time is controlled optimally on the basis of operation conditions of the internal combustion engine, generation of multiple discharge and consumption of the spark plug electrodes are suppressed to thereby extend the service life of the spark plug. In addition, occurrence of misfire can be suppressed.
  • the spark-discharge interruption circuit when spark discharge of the spark plug is to be interrupted, the spark-discharge interruption circuit is operated in accordance with the spark-discharge interruption command signal for controlling the spark-discharge duration time.
  • the spark-discharge interruption circuit may include an electricity-supply resumption circuit connected in parallel to the switching means adapted to interrupt and resume the primary current flowing through the primary winding.
  • the electricity-supply resumption circuit includes spark-discharge interruption switching means for resuming supply of the primary current to the primary winding in accordance with the spark-discharge interruption command signal; and current adjustment means connected in series to the spark-discharge interruption switching means and adapted to reduce the primary current flowing through the primary winding, after resumption of supply of the primary current to the primary winding, so as to prevent the spark plug from generating spark discharge.
  • the spark-discharge interruption switching means of the electricity-supply resumption circuit is driven in accordance with the spark-discharge interruption command signal, to thereby resume the supply of electricity to the primary winding.
  • the primary current which flows through the primary winding upon resumption of electricity supply is not interrupted instantaneously, but is decreased gradually by the current adjustment means of the electricity-supply resumption circuit such that the spark plug does not generate spark discharge.
  • the current adjustment means gradually reduces the primary current which flows upon resumption of electricity supply, to thereby prevent generation of high voltage at the secondary winding when the resumed electricity supply is stopped.
  • the spark-discharge interruption circuit may be configured such that a switching element such as a thyristor or a mechanical relay is connected to the opposite ends of the primary winding in parallel thereto, and the opposite ends of the primary winding are short-circuited by means of the switching element.
  • a switching element such as a thyristor or a mechanical relay
  • the energy control means maintains at a substantially constant level the magnetic flux energy which is accumulated in the ignition coil by virtue of supply of electricity to the primary winding by means of the ignition control means. Therefore, even when the magnetic flux energy accumulated in the ignition coil changes, mainly due to variation in the power source voltage, the magnetic flux energy accumulated in the ignition coil is controlled at a substantially constant level by the energy control means. As a result, the constituent elements, such as spark-discharge interruption switching means, of the spark-discharge interruption circuit are not broken. Also, their durability is not deteriorated, which breakage or durability deterioration would otherwise occur due to accumulation of excess magnetic flux energy in the ignition coil at the time that the spark discharge is interrupted. Therefore, the reliability of the ignition apparatus can be enhanced.
  • the spark energy supplied to the spark plug is controlled by interrupting spark discharge performed on the basis of operation conditions of the internal combustion engine, useless consumption of the electrodes of the spark plug can be suppressed.
  • excessive magnetic flux energy is not accumulated in the ignition coil at the time of electricity being supplied to the primary winding by means of the ignition control means, problems such as breakage of a constituent element of the spark-discharge interruption circuit for interrupting spark discharge can be prevented.
  • the energy control means for maintaining the magnetic flux energy accumulated in the ignition coil at a substantially constant level may include electricity-supply-start timing delay means for detecting power source voltage output from the DC power source unit, for setting, on the basis of the power source voltage, an electricity-supply-start delay time representing a time by which start of supply of electricity to the primary winding is to be delayed, and for delaying by the electricity-supply-start delay time the timing at which the ignition control means starts supply of electricity to the primary winding.
  • the energy control means is configured such that the supply of electricity to the primary winding is not simply started in response to an ignition command signal which is output in accordance with operation conditions of the internal combustion engine, but the timing for starting supply of electricity to the primary winding before spark discharge is delayed in accordance with the power source voltage output from the DC power source unit.
  • Such electricity-supply-start timing delay means may be realized by means of a circuit configuration which can maintain the switching means in an OFF state irrespective of control of the ignition command signal by the ignition control means; e.g., a circuit configuration which can change or maintain the ignition command signal input to the switching means in a state which brings the switching means into an OFF state.
  • the electricity-supply-start timing delay means forcedly changes the state of the ignition command signal such that the switching means comes into an OFF state.
  • the ignition command signal whose state has been changed by the electricity-supply-start timing delay means is input to the switching means, and consequently the ignition control means becomes unable to control the switching means.
  • the ignition control means becomes unable to control the switching means.
  • supply of electricity to the primary winding is not started at the electricity-supply-start timing instructed by the ignition control means.
  • the electricity-supply-start timing delay means stops the forced control of the ignition command signal input to the switching means after elapse of the electricity-supply-start delay time
  • the ignition control means becomes able to control the switching means, and thus, the switching means comes into an ON state by virtue of control by the ignition control means.
  • supply of electricity to the primary winding is started.
  • the above-described operation enables delay of the timing of starting the supply of electricity until the electricity-supply-start delay time elapses from the electricity-supply-start timing determined by the ignition control means.
  • the electricity-supply-start timing delay means sets the electricity-supply-start delay time in accordance with the power source voltage, even when the power source voltage varies, the magnetic flux energy accumulated in the ignition coil can be maintained at a substantially constant level.
  • the electricity-supply-start delay time is preferably set such that the electricity-supply-start delay time increases with the power source voltage.
  • the electricity-supply-start timing delay means controls only timing for starting supply of electricity to the primary winding and does not change the timing of interrupting the primary current (i.e., ignition timing), and the ignition timing is determined by the ignition control means. Therefore, provision of the electricity-supply-start timing delay means exerts no influence on the ignition timing.
  • the ignition control means is typically realized by means of the internal processing of a main controller (ECU), which is constituted by a microcomputer mainly consisting of a CPU, RAM, ROM and an input/output section.
  • ECU main controller
  • a recent main controller provided on an internal combustion engine controls not only ignition but also many other items, such as fuel injection amount, air-fuel ratio, and fuel injection timing, on the basis of signals input from sensors (e.g., crank angle sensor) provided at different portions of the internal combustion engine. Therefore, the load imposed on the internal processing of the main controller has increased considerably.
  • the main controller when the main controller performs, in addition to various existing control processes, a series of processes for interrupting spark discharge and a process for delaying the timing of starting supply of electricity to the primary winding, the processing load may increase, with the result that the main controller becomes unable to perform the various control processes properly.
  • the ignition control means comprises a main controller including the spark-discharge duration time setting means; and a signal processing unit including the electricity-supply-start timing delay means and the spark-discharge interruption control means.
  • the main controller sets an ignition timing and a spark-discharge duration time for each cylinder on the basis of operation conditions of the internal combustion engine, and generates a reference ignition command signal corresponding to the ignition timing.
  • the signal processing unit receives the reference ignition command signal output from the main controller and outputs to the switching means an ignition command signal which is delayed from the reference ignition command signal by the electricity-supply-start delay time, and generates, on the basis of the spark-discharge duration time set by the main controller, a spark-discharge interruption command signal to be output to the spark-discharge interruption circuit.
  • the processing for generating the reference ignition command signal on the basis of operation conditions of the internal combustion engine is performed in the main controller; and the processing for controlling the ignition command signal which is output to the switching means on the basis of the reference ignition command signal is performed in the signal processing unit.
  • the processing necessary for generation of spark discharge is effected in order to generate spark discharge.
  • the processing for setting the spark-discharge duration time is performed in the main controller; and the processing for controlling the spark-discharge interruption circuit is performed in the signal processing unit.
  • the processing for interrupting spark discharge is performed in order to control energy supplied to the spark plug.
  • the processing for delaying the timing of starting the supply of electricity to the primary winding in accordance with variation of the power source voltage is performed in the signal processing unit in order to maintain at a substantially constant level the magnetic flux energy accumulated in the ignition coil. This protects the constituent elements of the spark-discharge interruption circuit, while suppressing an increase in the processing load of the main controller.
  • the processing for generating spark discharge and the processing for interrupting spark discharge are executed while being distributed between the main controller and the signal processing unit, an increase in the processing load of the main controller is suppressed, and various types of control processing can be executed properly in the main controller.
  • the signal processing unit may include a signal path for outputting the reference ignition command signal directly to the switching means as an ignition command signal; and signal interruption means for breaking or disconnecting, if necessary, the signal path for outputting the reference ignition command signal directly to the switching means. That is, when the signal path is broken or disconnected by means of the signal interruption means, the ignition command signal is not output in accordance with the reference ignition command signal.
  • the signal path is connected again upon elapse of the electricity-supply-start delay time from the time at which the supply of electricity is instructed by the reference ignition command signal.
  • the timing of starting the supply of electricity to the primary winding can be delayed.
  • the switching means can be controlled directly in accordance with the reference ignition command signal from the main controller. Therefore, at least generation of spark discharge can be effected in order to continue the operation of the internal combustion engine.
  • wire lines for sending the reference ignition command signal and the spark-discharge duration time from the main controller to the signal processing unit must be provided.
  • the number of input terminals or output terminals is desirably decreased in order to reduce occupation areas.
  • a configuration as described in a fifth aspect of the invention is preferably employed in order to communicate to the signal processing unit the spark-discharge duration time set by the main controller. That is, in order to communicate to the signal processing unit the spark-discharge duration time set by the spark-discharge duration time setting means, while maintaining the form of a portion of the reference ignition command signal used to communicate an ignition timing, the main controller changes the form of another portion of the reference ignition command signal in order to include information representing the spark-discharge duration time; and the signal processing unit reads the spark-discharge duration time from the reference ignition command signal output from the main controller and generates the spark-discharge interruption command signal on the basis of the spark-discharge duration time.
  • a signal path for sending a reference ignition command signal is provided between the main controller and the signal processing unit; and the form of the reference ignition command signal is changed in order to include information representing the spark-discharge duration time, to thereby communicate from the main controller to the signal processing unit the spark-discharge duration time, as well as the ignition timing. Since the form of the portion of the reference ignition command signal used for communicating an ignition timing is maintained, even when the form of reference ignition command signal is changed in order to communicate the spark-discharge duration time, an erroneous ignition timing is not communicated to the signal processing unit.
  • the number of input or output terminals can be reduced in order to simplify the structure of the ignition apparatus.
  • the form of the reference ignition command signal is preferably changed such that the pulse width of the pulse signal is changed so as to communicate the spark-discharge duration time. That is, the spark-discharge duration time is communicated from the main controller to the signal processing unit by use of a notification reference ignition command signal having a pulse width different from that of the ordinary reference ignition command signal.
  • a rule for defining the relationship between the spark-discharge duration time and the number of continuously-output notification reference ignition command signals or the relationship between the spark-discharge duration time and the pulse width of a notification reference ignition command signal is determined in advance; and the main controller communicates the spark-discharge duration time to the signal processing unit by use of the notification reference ignition command signal(s) and in accordance with the rule.
  • the spark-discharge interruption control means detects the spark-discharge duration time from the number of continuously-output notification reference ignition command signals or the pulse width of the notification reference ignition command signal. Subsequently, the spark-discharge interruption control means interrupts spark discharge when the spark-discharge duration time has elapsed after generation of spark discharge.
  • the ignition apparatus for an internal combustion engine eliminates the necessity of providing a wiring line between the main controller and the signal processing unit in order to communicate the spark-discharge duration time only.
  • the structure of the ignition apparatus can be simplified, and packaging efficiency can be improved.
  • the pulse width of the notification reference ignition command signal corresponds to the primary-current supply period before spark discharge, generation of spark discharge may become difficult if the pulse width of the notification reference ignition command signal is excessively narrow. Therefore, the pulse width of the notification reference ignition command signal is preferably set wider than the narrowest pulse width necessary for generation of spark discharge.
  • the sequence of spark-discharge generation timings (i.e., ignition timings) of the respective cylinders is constant. Since the sequence of ignition timings of the plurality of cylinders is fixed, the internal combustion engine can be operated when the spark plugs provided for the respective cylinders are caused to generate spark discharge in a predetermined sequence, one spark plug at a time, every time a signal representing the ignition timings of all the cylinders is output after detection of the ignition timing of a certain cylinder.
  • the signal processing unit of the ignition apparatus provided for an internal combustion engine having a plurality of cylinder preferably comprises: signal processing control means for executing at least the processing of the spark-discharge interruption control means and the processing of the electricity-supply-start timing delay means; a first signal path for supplying to the signal processing control means at least one of the reference ignition command signals for the respective cylinders output from the main controller; and a second signal path for supplying to the signal processing control means a synthesized ignition command signal obtained through synthesis of all the reference ignition command signals output from the main controller, wherein the signal processing control means uses, as a reference, a time at which the reference ignition command signal is input from the first signal path, and outputs ignition command signals for the respective cylinders in a predetermined sequence such that one ignition command signal is output every time the synthesized ignition command signal is input from the second signal path.
  • the signal processing control means of the signal processing unit receives, via the first signal path, a reference ignition command signal used for identifying the ignition timing of a certain cylinder, and receives, via the second signal path, a synthesized ignition command signal which represents the ignition timings of all the cylinders.
  • the signal processing control means can use, as a reference, the reference ignition command signal for the predetermined single cylinder, and output ignition command signals for the respective cylinders in a predetermined sequence such that one ignition command signal is output every time the synthesized ignition command signal is input.
  • spark discharge can be generated at a proper timing in each cylinder to thereby operate the internal combustion engine.
  • ignition command signals for the respective cylinders can be output at proper timings even when the number of input terminals of the signal processing control means; i.e., the number of input terminals for inputting the reference ignition command signals, is less than the number of the cylinders of the internal combustion engine.
  • the ignition apparatus for an internal combustion engine can reduce the number of input terminals of the signal processing control means provided in the signal processing unit, to thereby increase the packaging density of the signal processing control means.
  • the synthesized ignition command signal is preferably obtained through logical addition (OR) of all the reference ignition command signals such that the synthesized ignition command signal enters an ON state when at least one of the reference ignition command signals enters an ON state.
  • the above-described ignition apparatus for an internal combustion engine (any one of the first through sixth aspects of the invention) achieves the effect more remarkably when the ignition apparatus is used for a gas engine using a gaseous fuel as described in a seventh aspect of the invention.
  • an ignition coil for a gas engine using a gaseous fuel must be designed such that the ignition coil generates a maximum secondary voltage (high voltage for ignition) higher than that for gasoline engines (e.g., whereas the maximum secondary voltage of an ignition coil for a gasoline engine is 30 kV or higher, the maximum secondary voltage of an ignition coil for a gasoline engine is 40 kV or higher).
  • the magnitude of current which is intermittently supplied to the primary winding of an ignition coil is set relatively high. Therefore, conceivably, a large amount of unnecessary spark energy may be supplied to the spark plug, to thereby further shorten the service life of the spark plug.
  • AC voltage (e.g., 100 or 200 V) supplied from a commercial power source such as an electric power company is converted to DC voltage by use of a transformer, a rectifier, a smoothing circuit, etc.; and the thus-obtained DC voltage is used to generate current to be supplied to the primary winding, to thereby generate high voltage for ignition.
  • the magnitude of DC voltage obtained from the AC voltage also changes seasonally. Therefore, in the case of a stationary gas engine, the power source voltage used for generating current to be supplied to the primary winding changes seasonally.
  • the period for supplying primary current is determined in consideration of a case in which the ignitability of fuel is at its poorest level, the period for supplying primary current is determined on the basis of the magnitude of DC voltage in a season in which the magnitude of DC voltage becomes lowest (i.e., primary current becomes smallest). In this case, during seasons in which the magnitude of DC voltage increases, the primary current becomes excessive even when the primary-current supply period is controlled properly, thereby increasing the possibility of the switching means generating excessive heat.
  • the effects of the present invention can be achieved more remarkably. That is, since the magnetic flux energy accumulated in the ignition coil is maintained at a substantially constant level, it is possible to prevent excessive current from flowing through a transistor for a long period, to thereby protect the switching means.
  • FIG. 1 is a diagram showing the configuration of a portion of an engine igniter according to a first embodiment of the invention corresponding to the first cylinder.
  • FIG. 2 is a circuit diagram showing the detailed configuration of the main control transistor 15 and the transistor 85 .
  • FIG. 3 is a time chart showing the states of respective portions of the engine igniter according to the first embodiment.
  • FIG. 4 is a schematic diagram showing the configuration of the engine igniter according to the first embodiment.
  • FIG. 5 is a flowchart showing the details of electricity-supply-start timing delay control processing.
  • FIG. 6 is a flowchart showing the details of spark-discharge interruption control processing.
  • FIG. 7 is a diagram showing the configuration of the signal processing unit 21 of an engine igniter according to a second embodiment of the invention.
  • FIG. 8 is a schematic diagram showing the configuration of an engine igniter according to a third embodiment of the invention.
  • FIG. 9 is a time chart showing the states of respective portions of the engine igniter according to the third embodiment.
  • FIG. 10 is a diagram showing the configuration of the signal processing unit 21 of an engine igniter according to a fourth embodiment of the invention.
  • FIG. 11 is a diagram schematically showing the configuration of an engine igniter according to a fifth embodiment of the invention.
  • FIG. 12 is a diagram showing the configuration of a portion of the engine igniter according to the fifth embodiment corresponding to the first cylinder.
  • FIG. 13 is a time chart showing the states of respective portions of the engine igniter according to the fifth embodiment.
  • FIG. 1 is a diagram schematically showing the configuration of an ignition apparatus for an internal combustion engine (hereinafter also referred to as an “engine igniter”) according to one embodiment of the invention.
  • the engine igniter according to the present embodiment is an engine igniter for a stationary gas engine which uses gaseous fuel. This stationary gas engine has three cylinders.
  • the engine igniter 1 includes a DC power source unit 11 , which converts AC voltage from a commercial power source to DC voltage (e.g., 12 V) for spark discharge and outputs the DC voltage; an ignition coil 13 , which has a primary winding L 1 and a secondary winding L 2 ; a main control transistor 15 , which is an npn-type transistor connected in series to the primary winding L 1 ; a spark plug 17 , which forms a closed loop in cooperation with the secondary winding L 2 and generates spark discharge between a center electrode 17 a and a ground electrode 17 b ; an electricity-supply resumption circuit 51 , which resumes supply of primary current to the primary winding L 1 so as to interrupt spark discharge generated by the spark plug 17 ; a signal processing unit 21 , which outputs an ignition command signal to the main control transistor 15 in order to cause the spark plug 17 to generate spark discharge and also outputs a spark-discharge interruption command signal to the electricity-supply
  • FIG. 1 shows only the structural components for the first cylinder.
  • the ECU 31 shown in FIG. 1 controls the spark-discharge generation timing (ignition timing), fuel injection amount, engine speed, and other parameters of the internal combustion engine on the basis of operation conditions of the internal combustion engine.
  • the ECU 31 is constituted by a microcomputer, which mainly consists of a CPU, RAM, ROM and an input/output section.
  • the ECU 31 outputs to the signal processing unit 21 a first reference ignition command signal IG 1 for the first cylinder, a second reference ignition command signal IG 2 for the second cylinder, a third reference ignition command signal IG 3 for the third cylinder, and a spark duration signal Sc which represents a spark-discharge duration time common among all the cylinders.
  • the signal processing control circuit 23 of the signal processing unit 21 outputs a first ignition command signal Sa 1 to the main control transistor 15 corresponding to the first cylinder, and also outputs second and third ignition command signals Sa 2 and Sa 3 to respective main control transistors corresponding to the second and third cylinders. Further, the signal processing control circuit 23 outputs a first spark-discharge interruption command signal Sb 1 to the electricity-supply resumption circuit 51 corresponding to the first cylinder, and also outputs second and third spark-discharge interruption command signals Sb 2 and Sb 3 to respective electricity-supply resumption circuits corresponding to the second and third cylinders.
  • the power-source-voltage detection circuit 33 is constructed by two resistors connected in series.
  • a divided voltage Vs which is a fraction of the power source voltage obtained by the resistors (i.e., Vs is the electrical potential at the node between the two resistors) is output to the signal processing unit 21 (specifically, to the signal processing control circuit 23 ).
  • the resistances of the two resistors provided in the power-source-voltage detection circuit 33 are determined such that the range of variation of the divided voltage Vs corresponding to the range of variation of the power source voltage output from the DC power source unit 11 falls within an allowable range of voltage input to the input terminal of the signal processing control circuit 23 .
  • the divided voltage Vs varies between the lower limit and upper limit of the input range (e.g., 0 to 5 V) of the signal processing control circuit 23 in accordance with the value of the power source voltage.
  • the signal processing control circuit 23 can detect the power source voltage by multiplying the divided voltage Vs input thereto by the ratio of the power source voltage to the divided voltage Vs, which is determined by the respective resistances of the two resistors provided in the power-source-voltage detection circuit 33 .
  • One end of the primary winding L 1 of the ignition coil 13 is connected to the positive terminal of the DC power source unit 11 , and the other end of the primary winding L 1 is connected to the collector 15 c of the main control transistor 15 .
  • One end of the secondary winding L 2 is connected via a rectifying element D to the one end of the primary winding L 1 , which is connected to the positive terminal of the DC power source unit 11 , and the other end of the secondary winding L 2 is connected to the center electrode 17 a of the spark plug 17 .
  • the ground electrode 17 b of the spark plug 17 is connected to ground, which has the same potential as that of the negative terminal of the DC power source unit 11 .
  • the base 15 b of the main control transistor 15 is connected to an output terminal of the signal processing control circuit 23 from which the first ignition command signal Sa 1 is output.
  • the emitter 15 e of the main control transistor 15 is connected to ground, which has the same potential as that of the negative terminal of the DC power source unit 11 .
  • the main control transistor 15 When the first ignition command signal Sa 1 input to the base 15 b of the main control transistor 15 is at a low level (typically, the ground potential), no base current flows in the main control transistor 15 , and consequently, the main control transistor 15 enters an OFF state. In this case, primary current i 1 does not flow through the primary winding L 1 via the main control transistor 15 .
  • the first ignition command signal Sa 1 is at a high level (e.g., voltage (5 V) supplied from the constant voltage power source)
  • the main control transistor 15 enters an ON state. In this case, a path for supplying electricity to the primary winding L 1 of the ignition coil 13 is formed.
  • the main control transistor 15 turns off to thereby stop (interrupt) supply of the primary current i 1 to the primary winding L 1 .
  • the magnetic flux density of the ignition coil 13 changes abruptly, and thus high voltage for ignition is generated from the secondary winding L 2 .
  • spark discharge is generated between the electrodes 17 a and 17 b of the spark plug 17 .
  • the ignition coil 13 is configured such that when primary current i 1 is intermittently supplied to the primary winding L 1 via the main control transistor 15 , high voltage for ignition which is negative relative to the ground potential is generated at the center electrode 17 a of the spark plug 17 .
  • secondary current i 2 flows from the center electrode 17 a of the spark plug 17 toward the primary winding L 1 side via the secondary winding L 2 .
  • the rectifying element D such as a diode, is provided at the connection portion between the secondary winding L 2 and the primary winding L 1 in order to permit flow of current from the secondary winding L 2 toward the primary winding L 1 and prevent flow of current in the opposite direction.
  • a diode serving as the rectifying element D is provided such that the anode of the diode is connected to the secondary winding L 2 and the cathode of the diode is connected o the primary winding L 1 .
  • the action of the rectifying element D prevents current from flowing into the secondary winding L 2 , which flow would otherwise occur when the main control transistor 15 is turned on (when supply of electricity to the primary winding L 1 is started).
  • the electricity-supply resumption circuit 51 includes an npn-type transistor 85 .
  • the emitter 85 e of the transistor 85 is grounded.
  • the base 85 b of the transistor 85 is connected to a terminal of the signal processing control circuit 23 from which the first spark-discharge interruption command signal Sb 1 is output.
  • the collector 85 c of the transistor 85 is connected to one connection end (electrode) of a capacitor 87 and is grounded via a diode 83 .
  • the anode of the diode 83 is grounded, and the cathode of the diode 83 is connected to the collector 85 c of the transistor 85 .
  • a connection end (electrode) of the capacitor 87 opposite the connection end (electrode) connected to the transistor 85 is connected via a resistor 91 to a node via which the collector 15 c of the main control transistor 15 is connected to the primary winding L 1 .
  • a diode 89 is connected in parallel to the resistor 91 .
  • the anode of the diode 89 is connected to a line extending between the resistor 91 and the primary winding L 1
  • the cathode of the diode 89 is connected to a line extending between the resistor 91 and the capacitor 87 .
  • the transistor 85 in the electricity-supply resumption circuit 51 enters an OFF state, and consequently, the electricity-supply resumption circuit 51 does not cause primary current i 1 to flow from the positive terminal of the DC power source unit 11 toward the primary winding L 1 .
  • the transistor 85 in the electricity-supply resumption circuit 51 enters an ON state, and consequently, the electricity-supply resumption circuit 51 forms a path for supplying electricity to the primary winding L 1 , which path starts from the positive terminal of the DC power source unit 11 , passes through the primary winding L 1 of the ignition coil 13 , and reaches the negative terminal of the DC power source unit 11 .
  • primary current i 1 flows through the primary winding L 1 .
  • the current flowing from the primary winding L 1 into the capacitor 87 flows through the diode 89 .
  • the primary current i 1 decreases gradually.
  • the flow of current through the capacitor 87 stops, and thus, the primary current i 1 is interrupted.
  • the capacitor 87 has been charged such that the electrode connected to the primary winding L 1 assumes a positive polarity and a potential difference greater than the voltage of the DC power source unit 11 is produced across the capacitor 87 , even when the first spark-discharge interruption command signal Sb 1 is at a high level, no primary current i 1 flows. Therefore, the charge accumulated in the capacitor 87 must be discharged in advance.
  • the first spark-discharge interruption command signal Sb 1 when the first spark-discharge interruption command signal Sb 1 is at a low level, the first ignition command signal Sa 1 for generation of high voltage for ignition is brought into a high level; i.e., the main control transistor 15 is brought into an ON state. Through this operation, the charge accumulated in the capacitor 87 can be discharged.
  • a closed loop is formed by the main control transistor 15 , the resistor 91 , the capacitor 87 , and the diode 83 . Since current flows through the closed loop due to charge accumulated in the capacitor 87 , the capacitor 87 is discharged. At this time, the current discharged from the capacitor 87 flows not through the diode 89 but through the resister 91 . Therefore, the current flowing through the closed loop decreases in amplitude, and thus the amount of current flowing through the main control transistor 15 is suppressed. This reduces the generation of heat by the main control transistor 15 at the time of discharging the charge accumulated in the capacitor 87 .
  • the electricity-supply resumption circuit 51 resumes supply of primary current i 1 to the primary winding L 1 to thereby interrupt the spark discharge of the spark plug 17 .
  • the electricity-supply resumption circuit 51 causes the primary current i 1 to decrease gradually with time, and eventually interrupts the primary current i 1 .
  • the level of the first ignition command signal Sa 1 is again changed to high in order to generate high voltage for the next ignition in the same cylinder, the charge accumulated in the capacitor 87 is discharged in preparation for subsequent spark discharge interruption.
  • each of the main control transistor 15 and the transistor 85 must have a large current amplification factor in order to supply a relatively large primary current i 1 in response to a small current output from the signal processing control circuit 23 , which is constituted by a microcomputer. Therefore, in actuality, each of the main control transistor 15 and the transistor 85 is configured by a circuit as shown by a circuit diagram of FIG. 2 . That is, each of the main control transistor 15 and the transistor 85 consists of three transistors; i.e., a first npn transistor Tr 1 , a second pnp transistor Tr 2 , and a third npn transistor Tr 3 . In the following, the circuit configuration will be de described while the main control transistor 15 is taken as an example.
  • a resister R 1 is connected to the base of the first transistor Tr 1 .
  • the base and emitter of the first transistor Tr 1 are mutually connected by a resistor R 2 .
  • the emitter of the first transistor Tr 1 is grounded.
  • the collector of the first transistor Tr 1 is connected to the base of the second transistor Tr 2 via a resistor R 3 .
  • An end of the resistor RI opposite the end connected to the base of the first transistor Tr 1 corresponds to the base terminal of the main control transistor 15 .
  • the base and emitter of the second transistor Tr 2 are mutually connected by a resistor R 4 .
  • the emitter of the second transistor Tr 2 is connected to a power source line LV, to which constant voltage is supplied.
  • the collector and emitter of the second transistor Tr 2 are mutually connected by a diode D 1 .
  • the collector of the second transistor Tr 2 is grounded via a resistor R 5 .
  • the anode of the diode D 1 is connected to the collector of the second transistor Tr 2 ; and the cathode of the diode D 1 is connected to the emitter of the second transistor Tr 2 .
  • the base of the third transistor Tr 3 is connected to the collector of the second transistor Tr 2 via a resistor R 6 .
  • the emitter of the third transistor Tr 3 corresponds to the emitter terminal 15 e of the main control transistor 15 .
  • the collector of the third transistor Tr 3 corresponds to the collector terminal 15 c of the main control transistor 15 .
  • the first transistor Tr 1 When the level of the signal input to the base terminal 15 b is low, the first transistor Tr 1 enters an OFF state, and the second transistor Tr 2 also enters an OFF state. Therefore, no current flows from the power source line LV to the third transistor, and consequently, the third transistor Tr 3 also enters an OFF state.
  • the circuit shown in FIG. 2 operates as follows.
  • the signal input to the base terminal 15 b is at a high level, electrical continuity is established between the collector terminal 15 c and the emitter terminal 15 e (i.e., the terminals 15 c and 15 e are short-circuited).
  • the signal input to the base terminal 15 b is at a low level, electrical continuity is not established between the collector terminal 15 c and the emitter terminal 15 e (i.e., the terminals 15 c and 15 e are isolated from each other).
  • the circuit shown in FIG. 2 operates in the same manner as a single npn transistor. Further, since three transistors are combined, the circuit has a high current amplification factor. Therefore, the main control transistor 15 , which has a circuit configuration shown in FIG. 2, can be driven by small current output from the signal processing control circuit in order to supply primary current i 1 .
  • the transistor 85 also has a circuit configuration shown in FIG. 2 .
  • the base 85 b corresponds to the base 15 b of the main control transistor 15 ;
  • the emitter 85 e corresponds to the emitter 15 e of the main control transistor 15 ;
  • the collector 85 c corresponds to the collector 15 c of the main control transistor 15 .
  • FIG. 4 shows a schematic configuration of the engine igniter 1 according to the present embodiment which includes primary-coil drive circuits, electricity-supply resumption circuits, ignition coils, and spark plugs for three cylinders.
  • the first primary-coil drive circuit 15 corresponds to the main control transistor 15 shown in FIG. 1;
  • the first ignition coil 13 corresponds to the ignition coil 13 shown in FIG. 1;
  • the first spark plug 17 corresponds to the spark plug 17 shown in FIG. 1;
  • the first electricity-supply resumption circuit 51 corresponds to the electricity-supply resumption circuit 51 shown in FIG. 1 .
  • the first through third ignition command signals Sa 1 to Sa 3 output from the signal processing control circuit 23 are fed to the first primary-coil drive circuit 15 , the second primary-coil drive circuit 115 , and the third primary-coil drive circuit 215 , respectively. Further, the first through third spark-discharge interruption command signals Sb 1 to Sb 3 output from the signal processing control circuit 23 are fed to the first electricity-supply resumption circuit 51 , the second electricity-supply resumption circuit 151 , and the third electricity-supply resumption circuit 251 , respectively.
  • the first primary-coil drive circuit 15 and the first electricity-supply resumption circuit 51 provided for the first cylinder are connected to the first ignition coil 13 and control intermittent supply of electricity to the primary winding L 1 of the first ignition coil 13 to thereby cause the first spark plug 17 to generate spark discharge and to interrupt the spark discharge.
  • the second primary-coil drive circuit 115 and the second electricity-supply resumption circuit 151 provided for the second cylinder are connected to the second ignition coil 113 .
  • the third primary-coil drive circuit 215 and the third electricity-supply resumption circuit 251 provided for the third cylinder are connected to the third ignition coil 213 .
  • the second spark plug 117 is connected to the second ignition coil 113 ; and the third spark plug 217 is connected to the third ignition coil 213 .
  • the second and third primary-coil drive circuits 115 and 215 are configured in the same manner as the main control transistor 15 shown in FIG. 1; the second and third ignition coils 113 and 213 are configured in the same manner as the ignition coil 13 shown in FIG. 1; the second and third spark plugs 117 and 217 are configured in the same manner as the spark plug 17 shown in FIG. 1; and the second and third electricity-supply resumption circuits 151 and 251 are configured in the same manner as the electricity-supply resumption circuit 51 shown in FIG. 1 .
  • the engine igniter 1 configured in the above-described manner generates and interrupts spark discharge in each of the three cylinders to thereby operate the internal combustion engine.
  • FIG. 3 shows a time chart representing variations with time in the first reference ignition command signal IG 1 , the first ignition command signal Sa 1 , potential Vp of the center electrode 17 a of the spark plug 17 , the first spark-discharge interruption command signal Sb 1 , primary current i 1 flowing through the primary winding L 1 , current i 4 flowing through the main control transistor 15 , and current i 3 flowing through the capacitor 87 , all of which appear in the circuit diagram for the first cylinder illustrated in FIG. 1 .
  • the level of the first reference ignition command signal IG 1 is switched from low to high at time t 1 shown in FIG. 3 . Subsequently, on the basis of the power source voltage detected by the power-source-voltage detection circuit 33 , the level of the first ignition command signal Sa 1 is switched from low to high at time t 2 ; i.e., when an electricity-supply-start delay time Ts set by the signal processing control circuit 23 has elapsed. As a result, the main control transistor 15 enters an ON state, and thus, primary current i 1 starts to flow through the primary winding L 1 of the ignition coil 13 .
  • a closed loop is formed by the capacitor 87 , the resistor 91 , the main control transistor 15 , and the diode 83 to thereby discharge the charge that has been accumulated in the capacitor 87 due to primary current re-supplied at the time of interruption of spark discharge during a previous combustion cycle of the cylinder. Therefore, current i 4 flows from the capacitor 87 while passing through the resistor 91 , the main control transistor 15 , and the diode 83 , in this sequence.
  • the direction of current i 3 flowing from the resistor 91 toward the capacitor 87 is assumed to be a positive direction. Therefore, the current i 3 flowing during the above-described discharge period is negative current.
  • both the primary current i 1 flowing through the primary winding L 1 and the current i 3 flow into the collector of the main control transistor 15 . Therefore, the current i 4 flowing through the main control transistor 15 assumes a waveform resulting from superposition of the current i 3 on the primary current i 1 .
  • the magnitude of the current i 4 is desirably decreased by reducing the magnitude of the current i 3 . Therefore, the resistance of the resistor 91 is preferably set so as to decrease the current i 3 . However, the resistance of the resistor 91 is desirably set such that the capacitor 87 can be discharged completely within a period in which the first ignition command signal Sa 1 is at a high level (a period from t 2 to t 3 ).
  • the level of the first spark-discharge interruption command signal Sb 1 is changed from low to high at time t 4 shown in FIG. 3 at which the spark discharge of the spark plug 17 continues.
  • transistor 85 turns on, and thus, a current path is formed which starts from the positive terminal of the DC power source unit 11 , passes through the primary winding L 1 of the ignition coil 13 and the electricity-supply resumption circuit 51 , and ends at the negative terminal of the DC power source unit 11 , resulting in resumption of supply of the primary current i 1 to the primary winding L 1 .
  • the spark discharge of the spark plug 17 is interrupted.
  • the current path within the electricity-supply resumption circuit 51 is formed by the diode 89 , the capacitor 87 , and the transistor 85 ; as charge is accumulated in the capacitor 87 , the primary current i 1 decreases gradually; and when the charging is completed after accumulation of a predetermined amount of charge in the capacitor 87 , the flow of the primary current i 1 stops.
  • the capacitor 87 Since the charge accumulated in the capacitor 87 is discharged before time t 3 , at time t 4 , the capacitor 87 permits the primary current i 1 to flow therethrough at a level necessary to interrupt the spark discharge.
  • supply of electricity to the primary winding L 1 is started when an electricity-supply-start delay time set in accordance with the power source voltage output from the DC power source unit 11 has elapsed (time t 2 in FIG. 3) after the time (time t 1 in FIG. 3) at which supply of electricity to the primary winding L 1 is started and which is set in accordance with the operation conditions of the internal combustion engine.
  • the electricity-supply-start delay time is set in the signal processing control circuit 23 . The details of the process which is performed in the signal processing control circuit 23 in order to set the electricity-supply-start delay time will be described below.
  • the ECU 31 totally controls the spark-discharge generation timing, fuel injection amount, idle engine speed, etc., of the internal combustion engine.
  • the ECU 31 performs operation condition detection processing for detecting operation conditions of various sections of the engine, such as intake air amount (intake pipe pressure), engine speed, throttle opening, coolant temperature, and intake air temperature; and fuel control processing for supplying fuel to the intake pipe at a fuel injection timing.
  • the ignition control processing is performed once during each combustion cycle, including intake, compression, combustion, and exhaust, of the internal combustion engine, on the basis of, for example, a signal from a crank-angle sensor for detecting the rotational angle of the engine (crank angle).
  • the ignition control processing is performed for each cylinder, and in the following description, the ignition control processing for the first cylinder will be described.
  • the ignition control processing When the ignition control processing is started upon startup of the internal combustion engine, operation conditions of the internal combustion engine detected by the operation condition detection processing performed separately are read. Subsequently, an ignition timing suitable for the operation conditions of the internal combustion engine is set on the basis of the operation conditions that have been read and by use of a previously prepared map or calculation formula. Thus, the ignition timing in the present combustion cycle is set.
  • the above-described map or calculation formula for setting an ignition timing is preferably configured such that an ignition timing suitable for the operation conditions of the internal combustion engine is determined while the operation conditions of the internal combustion engine such as engine speed and engine load are used as parameters.
  • the ignition control processing changes the level of the first reference ignition command signal IG 1 to high at a time which is earlier than the ignition timing by a predetermined period of time.
  • the predetermined period of time serves as a primary-current supply period before generation of spark discharge.
  • the primary-current supply period is preset such that sufficiently large magnetic flux energy is accumulated in the ignition coil during that period.
  • the spark discharge duration time i.e., a period of time from generation of spark discharge to natural termination of the spark discharge, becomes sufficiently long.
  • supply of electricity to the primary winding L 1 is actually started when the electricity-supply-start delay time has elapsed (time t 2 shown in FIG. 3) after the level of the first reference ignition command signal IG 1 has been changed to high. That is, when the signal processing control circuit 23 changes the level of the first ignition command signal Sa 1 to high, the main control transistor 15 enters an ON state to start supply of electricity to the primary winding L 1 .
  • the ignition control processing changes the level of the first reference ignition command signal IG 1 to low when the primary-current supply period has elapsed after the level of the first reference ignition command signal IG 1 has been changed to high. Simultaneously with this, the signal processing control circuit 23 changes the level of the first ignition command signal Sa 1 to low in order to bring the main control transistor 15 into an OFF state.
  • the main control transistor 15 enters the OFF state the primary current i 1 is interrupted abruptly, and thus, high voltage for ignition, which is induced electromotive force, is generated at the secondary winding L 2 , whereby the spark plug 17 generates spark discharge.
  • the ignition control processing sets an ignition timing in accordance with operation conditions of the internal combustion engine, and changes the level of the first reference ignition command signal IG 1 to high at a time which is earlier than the ignition timing by a predetermined primary-current supply period. Subsequently, when the primary-current supply period has elapsed; i.e., at the ignition timing set in accordance with the operation conditions of the internal combustion engine, the ignition control processing changes the level of the first reference ignition command signal IG 1 to low in order to cause the spark plug 17 to generate spark discharge between the electrodes thereof, to thereby burn fuel.
  • the spark-discharge duration time setting processing is started simultaneously with the startup of the internal combustion engine.
  • the spark-discharge duration time setting processing is not performed on a cylinder-by-cylinder basis, but a spark-discharge duration time common among all the cylinders is set.
  • the spark-discharge duration time setting processing first judges whether the internal combustion engine has been warmed up sufficiently. When the warm-up is judged to be insufficient, the spark-discharge duration time is set to 0 sec.
  • the operation conditions (engine speed, engine load, etc.) of the internal combustion engine separately detected by the operation condition detection processing are read.
  • a spark-discharge duration time Tc suitable for the operation conditions of the internal combustion engine is set on the basis of the operation conditions that have been read and by use of a previously prepared map or calculation formula.
  • the above-described map or calculation formula for setting a spark-discharge duration time Tc is preferably defined on the basis of, for example, several measurement data sets, such that a spark-discharge duration time Tc suitable for the operation conditions of the internal combustion engine is determined, while at least the engine speed and the engine load are used as parameters.
  • the spark-discharge duration time setting processing performs at constant intervals the above-described series of reading the operation conditions of the internal combustion engine and setting the spark-discharge duration time Tc by use of a map or calculation formula. Further, every time the spark-discharge duration time Tc is changed, the spark-discharge duration time setting processing outputs a spark duration signal Sc to the signal processing unit 21 in order to communicate the spark-discharge duration time Tc thereto.
  • a spark duration signal Sc floating-point numerical data representing the spark-discharge duration time Tc is preferably used as the spark duration signal Sc.
  • the spark-discharge duration time setting processing performs processing for setting a spark-discharge duration time Tc suitable for the operation conditions of the internal combustion engine, and for communicating the spark-discharge duration time Tc to the signal processing unit 21 by use of the spark duration signal Sc.
  • ignition signal control processing performed by the signal processing control circuit 23 of the signal processing unit 21 will be described. Notably, in the following description, only the ignition signal control processing for the first cylinder will be described; however, similar ignition signal control processing is performed for the second and third cylinders.
  • the ignition signal control processing When started upon startup of the internal combustion engine, the ignition signal control processing sets the level of the first ignition command signal Sa 1 in accordance with the level of the first reference ignition command signal IG 1 , which is input from the ECU 31 via the first IG signal input circuit 25 .
  • the ignition signal control processing changes the level of the first ignition command signal Sa 1 in order to start and stop supply of electricity to the primary winding L 1 at a timing for starting supply of electricity to the primary winding L 1 and an ignition timing, respectively. Both timings are set by the ignition control processing of the ECU 31 in accordance with the operation conditions of the internal combustion engine.
  • the level of the first ignition command signal Sa 1 is basically determined by the ignition signal control processing.
  • the first ignition command signal Sa 1 is set to a low level by means of electricity-supply-start timing delay control processing, which will be described below, priority is given to control by the electricity-supply-start timing delay control processing, and thus, the first ignition command signal Sa 1 is maintained at the low level.
  • this also holds true for the second and third ignition command signals Sa 2 and Sa 3 .
  • the electricity-supply-start timing delay control processing performed by the signal processing control circuit 23 will be described with reference to the flowchart shown in FIG. 5 .
  • the electricity-supply-start timing delay control processing is started for each cylinder.
  • the electricity-supply-start timing delay control processing for the first cylinder will be described.
  • step S 110 a counter value N is set to zero to thereby reset the counter value N.
  • the counter value N is used for determining a timing for detecting power source voltage.
  • the electricity-supply-start delay time Ts is set to an initial value, desirably to a value suitable for the operation conditions of the internal combustion engine immediately after the startup thereof. Since the temperature of the internal combustion engine is low immediately after startup, ignitability of fuel is poor. Therefore, the electricity-supply-start delay time Ts is preferably set to zero or a value such that the primary-current supply period becomes long.
  • step S 130 a judgment is made as to whether the first reference ignition command signal IG 1 output from the ECU 31 has risen (from low level to high level).
  • processing proceeds to step S 140 .
  • the processing in step S 130 is performed repeatedly in order to wait until the level of the first reference ignition command signal IG 1 changes. That is, in step S 130 , a judgment is made as to whether the timing for supplying electricity to the primary winding L 1 has come, which is determined by the ignition control processing performed in the ECU 31 .
  • step S 140 the first ignition command signal Sa 1 is set to a low level (time t 1 in FIG. 3 ). As a result, the first ignition command signal Sa 1 input to the base of the main control transistor 15 is maintained at a low level. That is, the main control transistor 15 maintains the OFF state irrespective of the command from the ECU 31 .
  • step S 150 a timer is started for measuring a period of time which has elapsed since the level of the first reference ignition command signal IG 1 has changed (after the result of the judgment in step S 130 has become YES).
  • step S 160 a judgment is made as to whether the value of the timer started in step S 150 is equal to or greater than the electricity-supply-start delay time Ts.
  • processing proceeds to step S 170 .
  • the processing in step S 160 is performed repeatedly in order to wait until the timer value becomes equal to or greater than the electricity-supply-start delay time Ts. That is, in step S 160 , a judgment is made as to whether the electricity-supply-start delay time Ts has elapsed after the level of the first reference ignition command signal IG 1 has changed (after the result of the judgment in step S 130 has become YES).
  • step S 160 When the result of the judgment in step S 160 is YES, processing proceeds to step S 170 .
  • step 170 the processing for maintaining the first ignition command signal Sa 1 at the low level is ended (at time t 2 in FIG. 3 ). Therefore, the level of the first ignition command signal Sa 1 is determined by the ignition signal control processing.
  • the level of the first reference ignition command signal IG 1 output from the ECU 31 When the level of the first reference ignition command signal IG 1 output from the ECU 31 is high, the level of the first ignition command signal Sa 1 becomes high. As a result, the main control transistor 15 enters an ON state, and thus, primary current i 1 starts to flow through the primary winding L 1 .
  • the level of the first reference ignition command signal IG 1 is changed from high to low by means of the above-described ignition control processing, which is separately performed by the ECU 31 .
  • the level of the first ignition command signal Sa 1 changes to low in order to interrupt the primary current i 1 , whereby spark discharge is produced between the electrodes of the spark plug 17 (time t 3 in FIG. 3 ).
  • step S 180 the timer having started in step S 150 is stopped.
  • step S 190 the timer value is set to zero to thereby reset the timer.
  • step S 200 one is added to the counter value N (the counter value N is incremented) in order to update the counter value N.
  • step S 210 a judgment is made as to whether the counter value N is equal to or greater than 5.
  • processing proceeds to step S 220 .
  • the judgment result is NO, processing returns to step S 130 .
  • the present electricity-supply-start timing delay control processing detects power source voltage every five combustion cycles of the cylinder; and in step S 210 , a judgment is made as to whether a combustion cycle (timing) for detection of power source voltage has come.
  • step S 210 When the result of the judgment in step S 210 is NO, processing returns to step S 130 .
  • step S 130 an electricity-supply-start timing in the next combustion cycle set by the ECU 31 is detected. Subsequently, the processing in steps S 130 to S 210 is repeatedly performed until the counter value N becomes equal to or greater than 5; i.e., until the result of the judgment in step S 210 becomes YES. Thus, the electricity-supply-start timing in each combustion cycle is delayed by using the same electricity-supply-start delay time Ts.
  • step S 210 the magnitude of the power source voltage is calculated on the basis of the divided voltage Vs input from the power-source-voltage detection circuit 33 . That is, the magnitude of the power source voltage is calculated by multiplying the detected divided voltage Vs by the ratio of the power source voltage to the divided voltage Vs, which is determined by the respective resistances of the two resistors provided in the power-source-voltage detection circuit 33 .
  • the electricity-supply-start delay time Ts is set by use of a map or calculation formula which uses the magnitude of the power source voltage as a parameter.
  • the map or calculation formula which is used in step S 230 to determine the electricity-supply-start delay time Ts is prepared on the basis of, for example, results of a measurement performed in advance, such that substantially constant magnetic flux energy is accumulated in the ignition coil 13 ; i.e., an optimal electricity-supply-start delay time Ts is obtained in accordance with the magnitude of the power source voltage.
  • the map or calculation formula is configured such that the electricity-supply-start delay time Ts increases with the magnitude of the power source voltage.
  • step S 240 the counter value N used for detecting the timing for detection of the power source voltage is set to zero to thereby reset the counter value N.
  • the electricity-supply-start timing delay control processing controls the delay in the timing for starting supply of primary current i 1 , while using the electricity-supply-start delay time Ts set in step S 230 . Subsequently, the processing in steps S 130 to S 210 is performed repeatedly.
  • the electricity-supply-start timing delay processing has been performed using the same electricity-supply-start delay time Ts in five combustion cycles of the cylinder, the result of the judgment in step S 210 become YES, and processing proceeds to step S 220 .
  • the processing in steps S 220 to S 240 is repeated in order to update the electricity-supply-start delay time Ts.
  • the electricity-supply-start timing delay processing controls the timing for starting supply of primary current i 1 on the basis of a predetermined initial value of the electricity-supply-start delay time Ts immediately after startup of the internal combustion engine; subsequently detects power source voltage every five combustion cycles of the cylinder; and updates the electricity-supply-start delay time Ts on the basis of the detected power source voltage.
  • the electricity-supply-start timing delay processing delays the timing for starting supply of electricity to the primary winding L 1 on the basis of the latest value of the electricity-supply-start delay time Ts.
  • the spark-discharge interruption control processing is performed once every combustion cycle for each cylinder.
  • the spark-discharge interruption control processing is started when the reference ignition command signal IG for the corresponding cylinder has risen (from low level to high level) after startup of the internal combustion engine.
  • the spark-discharge interruption control processing for the first cylinder will be described.
  • step S 550 the spark-discharge duration time Tc communicated from the ECU 31 by means of the spark duration signal Sc is first read so as to be used in subsequent processing. Since the spark duration signal Sc is always output from the ECU 31 to the signal processing control circuit 23 , the spark-discharge interruption control processing fetches the spark-discharge duration time Tc by performing the processing in step S 550 and interrupts spark discharge.
  • step S 560 a judgment is made as to whether an ignition timing has come, on the basis of a change in the level of the first reference ignition command signal IG 1 (from high to low).
  • step S 570 processing proceeds to step S 570 .
  • the processing in step S 560 is performed repeatedly for the purpose of awaiting the ignition timing.
  • the ignition timing for the first cylinder has come, and the result of the judgment in step S 560 becomes YES, processing proceeds to step S 570 .
  • step S 570 the present time t is set to a time variable T 2 in order to memorize the time of the ignition timing.
  • step S 580 a judgment is made as to whether a value obtained through subtraction of the time variable T 2 from the present time t; i.e., the value of t ⁇ T 2 , is equal to the spark-discharge duration time Tc determined in step S 550 .
  • processing proceeds to step S 590 .
  • the processing at S 580 is performed repeatedly for the purpose of awaiting elapse of the spark-discharge duration time. That is, the processing in step S 580 detects a spark-discharge interruption timing; i.e., passage of the spark-discharge duration time Tc after the ignition timing detected in step S 560 .
  • step S 590 the spark-discharge interruption operation is performed. Specifically, the level of the first spark-discharge interruption command signal Sb 1 is changed to high (time t 4 in FIG. 3) in order to operate the electricity-supply resumption circuit 51 to thereby cause current (primary current i 1 ) to flow through the primary winding L 1 again. Thus, the spark discharge is interrupted.
  • the electricity-supply resumption circuit 51 When the electricity-supply resumption circuit 51 is operated by changing the level of the first spark-discharge interruption command signal Sb 1 to high, the flow of the primary current i 1 stops or decreases to a small level within a predetermined period of time (time t 5 in FIG. 3 ), which has been set previously. Upon passage of this predetermined period of time, the level of the first spark-discharge interruption command signal Sb 1 is changed to low. Subsequently, the processing in step S 590 is ended, and the spark-discharge interruption control processing is ended.
  • the spark-discharge interruption control processing reads the spark-discharge duration time Tc communicated from the ECU 31 ; and outputs the first spark-discharge interruption command signal Sb 1 at a spark-discharge interruption timing; i.e. when the spark-discharge duration time Tc has elapsed from the ignition timing, in order to operate the electricity-supply resumption circuit 51 to thereby interrupt spark discharge.
  • the main control transistor 15 corresponds to the switching means; the ignition control processing performed by the ECU 31 and the ignition signal control processing performed by the signal processing control circuit 23 correspond to the ignition control means; the transistor 85 corresponds to the spark-discharge interruption switching means; the capacitor 87 corresponds to the current adjustment means; the spark-discharge duration time setting processing performed by the ECU 31 corresponds to the spark-discharge duration time setting means; the spark-discharge interruption control processing performed by the signal processing control circuit 23 corresponds to the spark-discharge interruption control means; and the electricity-supply-start timing delay control processing performed by the signal processing control circuit 23 corresponds to the electricity-supply-start timing delay means.
  • the ECU 31 corresponds to the main controller; the signal processing unit 21 corresponds to the signal processing unit; and the signal processing control circuit 23 corresponds to the signal processing control means.
  • the signal processing unit 21 of the engine igniter outputs the first through third spark-discharge interruption command signals Sb 1 to Sb 3 in order to operate the electricity-supply resumption circuit 51 to thereby resume supply of primary current i 1 to the primary winding L 1 .
  • spark discharge is interrupted.
  • the spark-discharge duration time is shortened in order to cause the spark plug to reliably generate spark discharge through application of high voltage, while suppressing excessive supply of spark energy to the spark plug.
  • the spark-discharge duration time is increased in order to reliably burn the fuel-air mixture.
  • the supply of electricity to the primary winding L 1 is not necessarily started at the time that the first reference ignition command signal IG 1 is output. That is, during a period in which the electricity-supply-start timing delay control processing performed by the signal processing control circuit 23 maintains the first ignition command signal Sa 1 at a low level, the main control transistor 15 is maintained in an OFF state irrespective of the level of the first reference ignition command signal IG 1 , and thus electricity is not supplied to the primary winding L 1 .
  • the electricity-supply-start timing delay control processing controls only timing for starting supply of electricity to the primary winding and does not change ignition timing.
  • the engine igniter of the present embodiment causes the spark plug to generate spark discharge at an ignition timing which is determined by the ignition control processing performed by the ECU 31 .
  • FIG. 7 shows the signal processing unit 21 used in the engine igniter of the second embodiment.
  • the signal processing unit 21 of the second embodiment includes an IG signal synthesis circuit 29 , in addition to the signal processing control circuit 23 , the first IG signal input circuit 25 , the second IG signal input circuit 125 , the third IG signal input circuit 225 , and the spark-duration-signal input circuit 27 .
  • the IG signal synthesis circuit 29 receives the first through third reference ignition command signals IG 1 to IG 3 from the first IG signal input circuit 25 , the second IG signal input circuit 125 , and the third IG signal input circuit 225 , respectively. Further, the IG signal synthesis circuit 29 outputs a synthesized ignition command signal IGM to the signal processing control circuit 23 .
  • the IG signal synthesis circuit 29 sets the level of the synthesized ignition command signal IGM to high when at least one of the three reference ignition command signals IG is at high level, and sets the level of the synthesized ignition command signal IGM to low when all the three reference ignition command signals IG are at low level.
  • the signal processing control circuit 23 receives three signal transmitted from the ECU 31 ; i.e., the fist reference ignition command signal IG 1 , the spark duration signal Sc, and the synthesized ignition command signal IGM. Therefore, when the ECU 31 changes the level of the first reference ignition command signal IG 1 in order to generate spark discharge in the first cylinder, the level of the synthesized ignition command signal IGM changes together with the level of the first reference ignition command signal IG 1 . By contrast, when the ECU 31 changes the level of the second reference ignition command signal IG 2 or the third reference ignition command signal IG 3 in order to generate spark discharge in the second or third cylinder, only the level of the synthesized ignition command signal IGM changes.
  • spark discharge is always generated in the first cylinder, in the second cylinder, and in the third cylinder, in this sequence. Therefore, when the level of the first reference ignition command signal IG 1 and the level of the synthesized ignition command signal IGM change concurrently, the signal processing control circuit 23 detects this change as a reference ignition command signal for the first cylinder, and changes the level of the first ignition command signal Sa 1 in accordance with the level of the synthesized ignition command signal IGM.
  • the signal processing control circuit 23 detects this change as a reference ignition command signal for the second cylinder, and changes the level of the second ignition command signal Sa 2 in accordance with the level of the synthesized ignition command signal IGM. Subsequently, when the level of the synthesized ignition command signal IGM changes, the signal processing control circuit 23 detects this change as a reference ignition command signal for the third cylinder, and changes the level of the third ignition command signal Sa 3 in accordance with the level of the synthesized ignition command signal IGM.
  • the signal processing control circuit 23 of the second embodiment uses the first reference ignition command signal IG 1 for the first cylinder as a reference, and outputs an ignition command signal for the first cylinder, an ignition command signal for the second cylinder, and an ignition command signal for the third cylinder, in this sequence, each time the synthesized ignition command signal IGM is input to the signal processing control circuit 23 , to thereby generate spark discharge at proper timing in each of the cylinders.
  • the engine igniter of the second embodiment eliminates the necessity of inputting to the signal processing control circuit 23 reference ignition command signals for all the cylinders, the engine igniter of the second embodiment can operate the internal combustion engine by use of a signal processing control circuit having fewer input terminals as compared with the first embodiment.
  • the engine igniter of the second embodiment reduces the number of input terminals of the signal processing control circuit provided in the signal processing unit in order to reduce the area occupied by the signal processing control circuit, to thereby increase packaging density.
  • the first IG signal input circuit 25 corresponds to the first signal path; and the IG signal synthesis circuit 29 corresponds to the second signal path.
  • FIG. 8 is a diagram schematically showing the configuration of the engine igniter according to the third embodiment.
  • the engine igniter 1 includes the above-described signal processing unit 21 , a power-source-voltage detection circuit 33 , primary-coil drive circuits, ignition coils, spark plugs, and electricity-supply resumption circuits.
  • the engine igniter 1 further includes an unillustrated DC power source unit 11 and the above-described ECU 31 .
  • the primary-coil drive circuit, the ignition coil, the spark plug, and the electricity-supply resumption circuit are provided for each of the first through third cylinders.
  • the engine igniter of the third embodiment differs from that of the first embodiment only in the configuration and the processing of the signal processing unit 21 and the ECU 31 in relation to notification of the spark-discharge duration time Tc, the description will focus on portions which differ from those of the first embodiment.
  • the ECU 31 does not have an output terminal for outputting the spark duration signal Sc, and has output terminals for outputting to the signal processing unit 21 three signals; i.e., first through third reference ignition command signals IGSc 1 to IGSc 3 .
  • the ECU 31 communicates to the signal processing control circuit 23 the spark-discharge duration time Tc, which is set in accordance with operation conditions of the internal combustion engine. For example, for each value of the spark-discharge duration time Tc, the number of continuously output notification reference ignition command signals corresponding thereto is determined and stored in the form of a map; and the notification reference ignition command signal is output a plurality of times corresponding to a value of the spark-discharge duration time Tc, which is set in accordance with operation conditions of the internal combustion engine.
  • the number of continuously output notification reference ignition command signals is not counted on a cylinder-by-cylinder basis.
  • the first through third reference ignition command signals IGSc 1 to IGSc 3 may be output successively in such manner that the first through third reference ignition command signals IGSc 1 to IGSc 3 have a pulse width different from the ordinary pulse width and thus serve as notification reference ignition command signals.
  • the spark-discharge duration time Tc is communicated once during performance of a plurality of combustion cycles (e.g., once every 100 combustion cycles).
  • the signal processing unit 21 includes a signal processing control circuit 23 constituted by a microcomputer; a first IG signal input circuit 25 , a second IG signal input circuit 125 , and a third IG signal input circuit 225 , which form signal paths for respectively inputting the first through third reference ignition command signals IGSc 1 to IGSc 3 to the signal processing control circuit 23 .
  • the first IG signal input circuit 25 , the second IG signal input circuit 125 , and the third IG signal input circuit 225 play the role of the spark-duration-signal input circuit used in the first embodiment.
  • spark-discharge duration time read processing performed by the signal processing control circuit 23 will be described.
  • the spark-discharge duration time read processing is started upon startup of the internal combustion engine.
  • the spark-discharge duration time read processing is not performed on a cylinder-by-cylinder basis but is performed commonly among the cylinders in order to read a spark-discharge duration time common among the cylinders.
  • the spark-discharge duration time read processing reads a new spark-discharge duration time Tc output from the ECU 31 and updates the old spark-discharge duration time Tc. This updating operation is performed whenever a new spark-discharge duration time Tc is read every 100 combustion cycles.
  • the signal processing control circuit 23 of the third embodiment performs spark-discharged interruption control processing which differs in processing in step S 550 from the spark-discharged interruption control processing of the first embodiment shown in FIG. 6 . That is, in step S 550 of the spark-discharged interruption control processing performed in the present embodiment, the spark-discharge duration time Tc is not read from the spark duration signal Sc, but the spark-discharge duration time Tc updated by the spark-discharge duration time read processing is read for use in subsequent combustion cycles. In subsequent spark-discharged interruption control processing, processing identical with that in steps S 560 to S 590 of the first embodiment is performed. Thus, when the spark-discharge duration time Tc has elapsed after the corresponding ignition timing, the spark-discharged interruption is performed in order to interrupt spark discharge.
  • the spark-discharged interruption control processing of the third embodiment is performed once during each combustion cycle for each cylinder.
  • the spark-discharged interruption control processing is started when the reference ignition command signal IG for each cylinder has risen (from low level to high level).
  • FIG. 9 shows a time chart representing variations with time in the reference ignition command signals for the first through third cylinders, the signal obtained through logical addition (OR) of the reference ignition command signals for the respective cylinders, and the potentials of the center electrodes of the spark plugs 17 for the respective cylinders.
  • the signal obtained through logical addition (OR) of the reference ignition command signals which have been output from the ECU 31 during the period from t 33 to t 36 serve as notification reference ignition command signals having a pulse width Tspk greater than the pulse width Tn of an ordinary reference ignition command signal and represents that the spark-discharge duration time Tc is to be updated. Therefore, spark discharge generated after t 37 is interrupted upon elapse of a spark-discharge duration time Ttb, which is shorter than a spark-discharge duration time Tta after which the spark discharge ends naturally. That is, spark discharge generated after t 37 is interrupted upon elapse of the spark-discharge duration time Ttb after the corresponding ignition timing until the spark-discharge duration time Tc is updated.
  • an engine igniter will be described according to a fourth embodiment in which the signal processing control circuit 23 has a reduced number of input terminals as compared with the third embodiment. Since the fourth embodiment differs from the third embodiment only in the configuration of the signal processing unit 21 , the description will focus on portions which differ from those of the third embodiment.
  • the signal processing unit 21 of the fourth embodiment includes an IG signal synthesis circuit 29 , in addition to the signal processing control circuit 23 , the first IG signal input circuit 25 , the second IG signal input circuit 125 , and the third IG signal input circuit 225 .
  • the first IG signal input circuit 25 , the second IG signal input circuit 125 , and the third IG signal input circuit 225 play the role of the spark-duration-signal input circuit.
  • the IG signal synthesis circuit 29 receives the first through third reference ignition command signals IGSc 1 to IGSc 3 from the first IG signal input circuit 25 , the second IG signal input circuit 125 , and the third IG signal input circuit 225 , respectively. Further, the IG signal synthesis circuit 29 outputs a synthesized ignition command signal IGScM to the signal processing control circuit 23 .
  • the IG signal synthesis circuit 29 sets the level of the synthesized ignition command signal IGScM to high when at least one of the three reference ignition command signals is at high level, and sets the level of the synthesized ignition command signal IGScM to low when all the three reference ignition command signals are at low level.
  • the signal processing control circuit 23 receives two signal transmitted from the ECU 31 ; i.e., the first reference ignition command signal IGSc 1 and the synthesized ignition command signal IGScM. Therefore, when the ECU 31 changes the level of the first reference ignition command signal IGSc 1 in order to generate spark discharge in the first cylinder, the level of the synthesized ignition command signal IGScM changes together with the level of the first reference ignition command signal IGSc 1 . By contrast, when the ECU 31 changes the level of the second reference ignition command signal IGSc 2 or the third reference ignition command signal IGSc 3 in order to generate spark discharge in the second or third cylinder, only the level of the synthesized ignition command signal IGScM changes.
  • spark discharge is always generated in the first cylinder, in the second cylinder, and in the third cylinder, in this sequence. Therefore, when the level of the first reference ignition command signal IGSc 1 and the level of the synthesized ignition command signal IGScM change concurrently, the signal processing control circuit 23 detects this change as a reference ignition command signal for the first cylinder, and changes the level of the first ignition command signal Sa 1 in accordance with the level of the synthesized ignition command signal IGScM.
  • the signal processing control circuit 23 detects this change as a reference ignition command signal for the second cylinder, and changes the level of the second ignition command signal Sa 2 in accordance with the level of the synthesized ignition command signal IGScM. Subsequently, when the level of the synthesized ignition command signal IGScM changes, the signal processing control circuit 23 detects this change as a reference ignition command signal for the third cylinder, and changes the level of the third ignition command signal Sa 3 in accordance with the level of the synthesized ignition command signal IGScM.
  • the signal processing control circuit 23 of the fourth embodiment uses the first reference ignition command signal IGSc 1 for the first cylinder as a reference, and outputs an ignition command signal for the first cylinder, an ignition command signal for the second cylinder, and an ignition command signal for the third cylinder, in this sequence, each time the synthesized ignition command signal IGScM is input to the signal processing control circuit 23 , to thereby generate spark discharge at proper timing in each of the cylinders.
  • the engine igniter of the fourth embodiment eliminates the necessity of inputting to the signal processing control circuit 23 reference ignition command signals for all the cylinders, the engine igniter of the fourth embodiment can operate the internal combustion engine by using a signal processing control circuit having fewer input terminals as compared with the third embodiment.
  • the signal processing control circuit 23 judges the pulse width of the synthesized ignition command signal IGScM to thereby count the number of continuously output notification reference ignition command signals, to thereby read the spark-discharge duration time Tc. Since the notification reference ignition command signal is detected from the synthesized ignition command signal IGScM, the processing which is performed within the signal processing control circuit 23 in order to obtain the result of logical addition (OR) of the reference ignition command signals for three cylinders can be omitted. Thus, an increase in processing load of the signal processing control circuit 23 can be suppressed.
  • the first IG signal input circuit 25 corresponds to the first signal path; and the IG signal synthesis circuit 29 corresponds to the second signal path.
  • FIG. 11 is a diagram schematically showing the configuration of the engine igniter according to the fifth embodiment.
  • the engine igniter 1 includes the above-described signal processing unit 21 , a power-source-voltage detection circuit 33 , primary-coil drive circuits, ignition coils, spark plugs, and electricity-supply resumption circuits.
  • the engine igniter 1 further includes an unillustrated DC power source unit 11 and the above-described ECU 31 .
  • the primary-coil drive circuit, the ignition coil, the spark plug, and the electricity-supply resumption circuit are provided for each of the first through third cylinders.
  • the signal processing unit 21 includes a signal processing control circuit 23 constituted by a microcomputer; a first IG signal input circuit 25 , a second IG signal input circuit 125 , and a third IG signal input circuit 225 , which form signal paths for respectively inputting the first through third reference ignition command signals IGSc 1 to IGSc 3 to the signal processing control circuit 23 ; and a first ignition-command-signal interruption circuit 35 , a second ignition-command-signal interruption circuit 135 , and a third ignition-command-signal interruption circuit 235 for breaking signal paths used for respectively outputting the first through third reference ignition command signals IGSc 1 to IGSc 3 directly to the first primary-coil drive circuit 15 , the second primary-coil drive circuit 115 , and the third primary-coil drive circuit 215 .
  • the signal processing unit 21 includes a signal path for outputting directly to the corresponding primary-coil drive circuit the reference ignition command signal received from the corresponding IG signal input circuit.
  • the first ignition-command-signal interruption circuit 35 is provided in the signal path extending from the first IG signal input circuit 25 of the signal processing unit 21 to the first primary-coil drive circuit 15 .
  • the first ignition-command-signal interruption circuit 35 maintains the continuity of the signal path extending from the first IG signal input circuit 25 to the first primary-coil drive circuit 15 (a connected state).
  • the first ignition-command-signal interruption circuit 35 breaks the signal path extending from the first IG signal input circuit 25 to the first primary-coil drive circuit 15 (a disconnected state).
  • the signal processing control circuit 23 reads the spark-discharge duration time Tc from notification ignition command signals having a pulse width different from an ordinary pulse width, among the first through third reference ignition command signals IGSc 1 to IGSc 3 . Subsequently, on the basis of the thus read spark-discharge duration time Tc, the signal processing control circuit 23 outputs the first spark-discharge interruption command signal Sb 1 to the electricity-supply resumption circuit 51 corresponding to the first cylinder. Further, the signal processing control circuit 23 outputs the second and third spark-discharge interruption command signals Sb 2 and Sb 3 to the electricity-supply resumption circuits corresponding to the second and third cylinders. In this manner, the signal processing control circuit 23 interrupts spark discharge in the respective cylinders by use of the spark-discharge duration time Tc communicated from the ECU 31 .
  • the signal processing control circuit 23 does not output ignition command signals (Sa 1 , Sa 2 , and Sa 3 ).
  • the signals output from the first, second, and third ignition-command-signal interruption circuit 35 , 135 , and 235 to the respective primary-coil drive circuits serve as the first through third ignition command signals Sa 1 , Sa 2 and Sa 3 , respectively.
  • the signal processing control circuit 23 can maintain the first through third ignition command signals Sa 1 , Sa 2 and Sa 3 at a low level. That is, the signal processing control circuit 23 can prevent the supply of primary current from starting when the corresponding reference ignition command signal is input from the ECU 31 and can delay the start of the supply of primary current.
  • step S 140 of the fifth embodiment the level of the first electricity-supply start delay signal Sd 1 is set high in order to bring the first ignition-command-signal interruption circuit 35 into a disconnected state, to thereby prevent the first reference ignition command signal IGSc 1 from being input to the first primary-coil drive circuit 15 . That is, by preventing the first ignition command signal Sa 1 from being controlled by the first reference ignition command signal IGSc 1 , the first primary-coil drive circuit 15 is maintained in an OFF state, regardless of the command from the ECU 31 , to thereby prohibit the supply of primary current.
  • step S 170 the level of the first electricity-supply start delay signal Sd 1 is set low in order to bring the first ignition-command-signal interruption circuit 35 into a connected state, to thereby permit the first reference ignition command signal IGSc 1 to be input to the first primary-coil drive circuit 15 . That is, by permitting the first ignition command signal Sa 1 to be controlled by the first reference ignition command signal IGSc 1 , the first primary-coil drive circuit 15 is maintained in an ON state, to thereby start the supply of primary current.
  • the electricity-supply-start timing delay control processing of the fifth embodiment controls the timing for starting supply of primary current i 1 on the basis of a predetermined initial value of the electricity-supply-start delay time Ts immediately after startup of the internal combustion engine; subsequently detects power source voltage every five combustion cycles of the cylinder; and updates the electricity-supply-start delay time Ts on the basis of the detected power source voltage.
  • the electricity-supply-start timing delay processing delays the timing for starting supply of electricity to the primary winding L 1 , on the basis of the latest value of the electricity-supply-start delay time Ts.
  • FIG. 12 is a block diagram showing a configuration of a portion of the engine igniter of the fifth embodiment corresponding to the first cylinder.
  • the engine igniter 1 of the fifth embodiment includes a DC power source unit 11 ; an ignition coil 13 ; a main control transistor 15 ; a spark plug 17 ; an electricity-supply resumption circuit 51 ; a signal processing unit 21 ; an electronic control unit (hereinafter referred to as an “ECU”) 31 ; and a power-source-voltage detection circuit 33 .
  • ECU electronice control unit
  • the signal processing unit 21 includes a signal processing control circuit 23 , which is constituted by a microcomputer; a first IG signal input circuit 25 ; a second IG signal input circuit 125 ; a third IG signal input circuit 225 ; an npn-type signal-interruption transistor 39 ; and a resistor 37 .
  • the signal-interruption transistor 39 and the resistor 37 serve as the first ignition-command-signal interruption circuit 35 shown in FIG. 11 .
  • the signal processing unit 21 includes signal-interruption transistors and resistors for the second and third cylinders.
  • the first IG signal input circuit 25 receives the first reference ignition command signal IGSc 1 from the ECU 31 and outputs it to the main control transistor 15 via the resistor 37 and to the signal processing control circuit 23 .
  • the signal input from the resistor 37 to the main control transistor 15 will be referred to as a first ignition command signal Sa 1 .
  • the base of the signal-interruption transistor 39 is connected to the output terminal of the signal processing control circuit 23 from which the first electricity-supply start delay signal Sd 1 is output; the emitter of the signal-interruption transistor 39 is grounded; and the collector of the signal-interruption transistor 39 is connected to a line extending from the resistor 37 to the base 15 b of the main control transistor 15 .
  • the signal-interruption transistor 39 When the first electricity-supply start delay signal Sd 1 input to the base of the signal-interruption transistor 39 is at low level (typically, ground potential), no base current flows into the signal-interruption transistor 39 , and consequently, the signal-interruption transistor 39 enters an OFF state.
  • the level of the first ignition command signal Sa 1 input to the base 15 b of the main control transistor 15 is determined on the basis of the level of the first reference ignition command signal IGSc 1 output from the ECU 31 .
  • the main control transistor 15 when the signal-interruption transistor 39 is in the OFF state, the main control transistor 15 is turned on and off in accordance with the first reference ignition command signal IGSc 1 output from the ECU 31 .
  • the first electricity-supply start delay signal Sd 1 is at high level (e.g., 5 V, which is voltage supplied from the constant voltage power source)
  • base current flows into the signal-interruption transistor 39 , and consequently, the signal-interruption transistor 39 enters an ON state.
  • the first ignition command signal Sa 1 is maintained at low level, and is not determined on the basis of the level of the first reference ignition command signal IGSc 1 output from the ECU 31 .
  • the signal-interruption transistor 39 is in the ON state, the main control transistor 15 is maintained OFF, irrespective of the first reference ignition command signal IGSc 1 output from the ECU 31 .
  • the main control transistor 15 is turned on and off in accordance with the command (the first reference ignition command signal IGSc 1 ) output from the ECU 31 .
  • the main control transistor 15 is in the OFF state at all times, irrespective of the level of the command (the first reference ignition command signal IGSc 1 ) output from the ECU 31 .
  • FIG. 13 shows a time chart representing variations with time in the first reference ignition command signal IGSc 1 , the first ignition command signal Sa 1 , the first electricity-supply start delay signal Sd 1 , the primary current i 1 , and the potential Vp of the center electrode 17 a of the spark plug 17 , all of which appear in the engine igniter of the fifth embodiment shown in FIG. 12 .
  • the level of the first reference ignition command signal IGSc 1 is switched from low to high at time t 1 shown in FIG. 13 .
  • the level of the first electricity-supply start delay signal Sd 1 is switched from low to high on the basis of the divided voltage Vs of the power source voltage detected by the power-source-voltage detection circuit 33 .
  • the first ignition command signal Sa 1 is maintained at a low level, and therefore no primary current i 1 flows through the primary winding L 1 .
  • the level of the first electricity-supply start delay signal Sd 1 is switched to low.
  • the level of the first ignition command signal Sa 1 is switched to high, and therefore the main control transistor 15 enters an ON state, with the result that the primary current i 1 flows through the primary winding L 1 .
  • the primary current i 1 does not flow, insofar as the level of the first electricity-supply start delay signal Sd 1 is high. Therefore, the timing for starting the supply of primary current i 1 can be delayed by means of the first electricity-supply start delay signal Sd 1 .
  • the actual primary current supply period (from time t 2 to time t 3 ) is shorter than the primary current supply period (from time t 1 to time t 3 ) set by the ECU 31 .
  • the signal processing control circuit 23 merely controls the timing for starting the supply of electricity to the primary winding L 1 and does not change the ignition timing; the ignition timing is determined by the ECU 31 . Therefore, provision of the signal processing control circuit 23 does not affect the ignition timing.
  • the signal processing control circuit 23 becomes unable to output the first electricity-supply start delay signal Sd 1 due to a certain cause, the signal-interruption transistor 39 enters an OFF state. Therefore, the main control transistor 15 is controlled by the ECU 31 in order to control supply and interruption of primary current i 1 , thereby enabling the operation of the internal combustion engine to continue.
  • the DC power source unit is not limited to a DC power source unit in which AC voltage from a commercial power source is converted into DC voltage; the engine igniter of the present invention can be practiced by use of a battery which outputs charged electrical energy in the form of DC voltage.
  • power source voltage is detected every five combustion cycles in order to update the electricity-supply-start delay time Ts.
  • this updating operation may be performed every ten combustion cycles, and the updating interval may be preferably set in accordance with the frequency of variation of the power source voltage.
  • the internal combustion engine is not limited to a gas engine using a gaseous fuel; the engine igniter of the present invention may be applied to an internal combustion engine using a liquid fuel such as gasoline.
  • Some of the above-described embodiments use a method for communicating a spark-discharge duration time by means of the number of continuously output notification reference ignition command signals.
  • the following method may be employed.
  • the relationship between pulse width and spark-discharge duration time Tc is previously stored in the form of a map; and a spark-discharge duration time is communicated by means of the pulse width of a single notification reference ignition command signal.

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JP4462747B2 (ja) 2010-05-12
EP1201920A2 (de) 2002-05-02
JP2002138934A (ja) 2002-05-17

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